Yes, active content will work, although if you intend to use our hacked active content, you naturally need to jailbreak... which might not be an option, depending on what firmware the device ships with.
The first thing you MUST do when receiving your Kindle, is to keep it offline and install the jailbreak, before you can get hit with an over-the-air upgrade to the latest 5.6.x firmware!
PDFs will be much more readable if you use the
KOReader alternative reader -- I can't say how well the builtin one works (I don't use it
) but definitely not as well.